Mixtures of optical isomers of aminopolycarboxylic acids represented by general formula (II) can be easily synthesized by organic synthetic techniques starting from various amines and maleic acid or fumaric acid. In the case of an optically active amino acid, however, optically active aspartic acid or the like must be used as the starting material in the organic synthesis. For example, it is reported that a mixture of the stereoisomers (S,S-, R,R- and meso-isomers) of a diaminoalkylene-N,N-disuccinic acid, which is a compound having two asymmetric carbon atoms in its molecule, can be chemically synthesized from maleic acid and various diamines (U.S. Pat. No. 3,158,635), while an optical isomer of this compound can be produced from L-aspartic acid and dibromoethane (John A. Neal et al., Inorganic Chem., 7, 2405 (1968)). However, L-aspartic acid and dibromoethane employed as the starting materials in the above process are relatively expensive, which makes it difficult to supply an inexpensive and commonly available optical isomer using said process.
With respect to microbial production, on the other hand, S,S-ethylenediamine-N,N'-disuccinic acid is isolated from the culture medium of Actinomycetes MG417-CF17A strain as a specific inhibitor of phospholipase C (T. Nishikiori et al., J. Antibiotics, 37, 426 (1984)). However, this microorganism only achieves an extremely low productivity. Thus, this production process is not industrially practical.
In contrast thereto, a novel process for efficiently producing an optically active diaminoalkylene-N,N'-disuccinic acid or the like from fumaric acid and various diamines using the catalytic action of a microorganism has been described (EP-A-0731171). An object of the present invention is to elevate the reaction yield in this process.